1. Field of the Invention
This invention relates to a refrigeration apparatus having ice making mechanism and in particular to means for controlling the timing of an ice making cycle.
2. Description of the Prior Art
In U.S. Pat. No. 3,648,478, which patent is owned by the assignee hereof, the inventor herein disclosed a defrost control utilizing a single timer motor for cyclically driving an ice maker and timing a series of defrost and refrigeration operations. The timer motor is connected alternatively in parallel with and in series with the compressor motor of the apparatus in effecting the desired control. The circuit of the control allows the timer motor to be energized during operation of the defrost heater and provides a fixed off time for the refrigeration apparatus during each defrosting operation, regardless of how long the defrost heater was actually energized. Operation of the defrost heater, in turn, is controlled by a thermally responsive bimetallic switch. The opening of the bimetallic switch is controlled by the temperature condition of the apparatus being heated by the defrost heater and, thus, the timer in this control runs for a variable amount of time during which the defrost heater is energized. The inclusion of this defrost time in the timing of the ice making cycle has been found to be undesirable as it represents a time interval during which ice making in the ice making apparatus is impaired. It is desirable that the water in the ice maker tray is completely frozen at the end of the timed ice making cycle and it has been found that this can be assured by eliminating from the timed operation of the timer the time interval during which the defrost heater is energized.
In another U.S. patent owned by the assignee hereof, namely U.S. Pat. No. 3,714,794 of William J. Linstromberg et al., the ice maker utilizes a similar control wherein the timer motor and defrost heater are connected in parallel during the defrost operation so that the timer remains on during the defrost period.
In U.S. Pat. No. 3,643,458 also owned by the assignee hereof, William J. Linstromberg et al disclose an ice maker having a separate ice maker timer motor and a defrost timer motor. The ice maker timer motor is effectively connected in parallel with the defrost heater during the defrost operation and connected in series with the defrost bimetallic switch.
In U.S. Pat. No. 3,964,269 of William J. Linstromberg, which patent is also owned by the assignee hereof, an ice maker apparatus is shown wherein the timer motor is continuously operated during the energization of the defrost heater by means of a double throw, double pole switch controlled by operation of the timer. Concurrently with throwing of the switch to effect connection of the defrost heater for energization thereof, the switch connects the timer motor in parallel therewith to continue the timing operation. The circuit is further arranged so that the defrost bimetal switch controlling operation of the defrost heater does not affect operation of the timer motor and, thus, the timer motor continues to operate until the end of the defrost time cycle notwithstanding the de-energization of the defrost heater by the defrost bimetal switch.